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We prospectively studied a cohort of 25 HIV-1 infected individuals with no clinical signs of encephalopathy with 99mTc-HMPAO-SPECT. The findings were correlated with magnetic resonance imaging (MRI), neuropsychological testing and clinical staging aiming at the early diagnosis of HIV encephalopathy by single photon emission computed tomography (SPECT). A total of 25 matched seronegative controls were subject to neuropsychological testing only. A total of 24 patients and controls were monitored for 6-46 months (mean and median 26 months). No patients developed AIDS dementia complex during the study; 3 patients developed minimal symptoms (MSK classification stage 0.5). There was a significant decline in 99mTc-HMPAO uptake over time and neuropsychological abnormalities progressed. Unexpectedly, there was a correlation of high cortical and subcortical 99mTc-HMPAO uptake and low performance in cognitive dysfunction tests, indicating a possible inflammatory reaction in the brain with increased blood flow due to HIV infection. We conclude that, in non-demented HIV-infected individuals, both the 99mTc-HMPAO uptake and functional level slowly decrease over time, but the regional cerebral blood flow decrease could be masked by a direct HIV-induced inflammatory reaction in the brain, which gives a 99mTc-HMPAO hyperfixation.

Three patients, two women and one man, aged 56-70 year (mean 59 years) with modest neurological deficits and bilateral occlusion of the common carotid arteries initially identified by duplex scanning and angiography were followed by repeated clinical and transcranial Doppler examination (TCD) over 6.5 years. Vasomotor reactivity (VMR) was tested by combined examination of TCD and xenon-133 cerebral blood flow (CBF) before and after intravenous administration of 1 g acetazolamide. At follow-up CBF was measured using single photon emission computerised tomography (SPECT). In two patients mean velocities in the middle cerebral artery (MCA) were within the normal range at repetitive examinations with good VMR ranging 30-111%, whereas CBF was reduced in MCA territories ranging 29-36 ml 100 g(-1) min(-1), but increasing 44-69% after acetazolamide, indicating good VMR. These 2 cases had anterograde flow in the ophthalmic artery and siphon. The third patient had very low MCA mean velocities of 21-27 cm sec(-1), increasing 26-33% after acetazolamide. This patient had retrograde flow in the ophthalmic artery and siphon connected with bilateral prolonged episodes of amaurosis fugax and transient ischemic attacks. In all three patients the posterior cerebral arteries were major supplying collaterals having high mean velocities of about 100 cm sec(-1) and high velocities in the basilar arteries of 85 cm sec(-1) as well. During follow up no patient had a new stroke, but all experienced orthostatic dizziness and chronic fatigue.

Cerebral blood flow (CBF) and the cerebral vasoreactivity was measured in patients with cerebrovascular disease and longstanding occlusion of the common carotid artery (CCA). In addition, regional CBF was correlated with transcranial doppler (TCD) measurements at baseline and during 6% CO2 inhalation and after intravenous administration of 1 g of acetazolamide. Twelve patients with a mean age of 62 years (range 45 to 71 years) were included, and the data compared to age-matched healthy controls. CBF was measured by intravenous injection of xenon-133 and SPECT (Tomomatic 564). TCD of the middle cerebral artery (MCA) was done by EME TC-64B. A very low global CBF value of 28 +/- 5 (SD) ml 100 g-1 min-1 was found at baseline as compared to 55 +/- 5 ml 100 g-1 min-1 in the normal controls. During 6% CO2-inhalation and after acetazolamide administration, CBF increased by 58 +/- 24% and 51 +/- 21%, respectively, indicating substantial collateral supply. Correlative analysis of CBF in the MCA territory and TCD in the MCA showed statistical significance only for the pooled data, i.e. compiling the data obtained during baseline and the two vasodilatory tests, and then only for the mean and peak TCD velocity (e.g. r = 0.59, p less than 0.002, n = 35, mean velocity, right side). We conclude that TCD measurements do not predict regional CBF in patients with CCA occlusion. The study emphasizes that these two methods yield supplementary information, with TCD measurements providing information of the circle of Willis and CBF studies of the flow distribution.